Limits...
Actin foci facilitate activation of the phospholipase C-γ in primary T lymphocytes via the WASP pathway.

Kumari S, Depoil D, Martinelli R, Judokusumo E, Carmona G, Gertler FB, Kam LC, Carman CV, Burkhardt JK, Irvine DJ, Dustin ML - Elife (2015)

Bottom Line: Yet, when WASP function is eliminated there is negligible effect on actin polymerization at the immunological synapse, leading to gaps in our understanding of the events connecting WASP and calcium ion signaling.These foci are polymerized de novo as a result of the T cell receptor (TCR) proximal tyrosine kinase cascade, and facilitate distal signaling events including PLCγ1 activation and subsequent cytoplasmic calcium ion elevation.We conclude that WASP generates a dynamic F-actin architecture in the context of the immunological synapse, which then amplifies the downstream signals required for an optimal immune response.

View Article: PubMed Central - PubMed

Affiliation: Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, United States.

ABSTRACT
Wiscott Aldrich Syndrome protein (WASP) deficiency results in defects in calcium ion signaling, cytoskeletal regulation, gene transcription and overall T cell activation. The activation of WASP constitutes a key pathway for actin filament nucleation. Yet, when WASP function is eliminated there is negligible effect on actin polymerization at the immunological synapse, leading to gaps in our understanding of the events connecting WASP and calcium ion signaling. Here, we identify a fraction of total synaptic F-actin selectively generated by WASP in the form of distinct F-actin 'foci'. These foci are polymerized de novo as a result of the T cell receptor (TCR) proximal tyrosine kinase cascade, and facilitate distal signaling events including PLCγ1 activation and subsequent cytoplasmic calcium ion elevation. We conclude that WASP generates a dynamic F-actin architecture in the context of the immunological synapse, which then amplifies the downstream signals required for an optimal immune response.

Show MeSH

Related in: MedlinePlus

Localization of phosphorylated form of Src family kinases (SFK) at TCR MC/F-actin foci.AND mouse CD4 T cell blasts were labeled with Alexa568-H57 Fab, incubated with MHCp/ICAM1 containing bilayer for 2 min, fixed and then immunostained for phospho-SFK (p-SFK). An example line scan profile for the line (white) indicated on the left image is displayed (right graph) to show the relative distribution of TCR, actin and phospho-SFK across the row of pixels. Scale bar, 6 μm.DOI:http://dx.doi.org/10.7554/eLife.04953.022
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4355629&req=5

fig3s2: Localization of phosphorylated form of Src family kinases (SFK) at TCR MC/F-actin foci.AND mouse CD4 T cell blasts were labeled with Alexa568-H57 Fab, incubated with MHCp/ICAM1 containing bilayer for 2 min, fixed and then immunostained for phospho-SFK (p-SFK). An example line scan profile for the line (white) indicated on the left image is displayed (right graph) to show the relative distribution of TCR, actin and phospho-SFK across the row of pixels. Scale bar, 6 μm.DOI:http://dx.doi.org/10.7554/eLife.04953.022

Mentions: To further investigate the role of TCR signaling in foci formation, we examined the role of Src family kinases (SFK) signaling. TCR signaling proceeds by accumulation of active Lck, as indicated by phosphorylation of the activation loop, in MCs (Campi et al., 2005). Consistent with this, phospho-SFK localized to F-actin foci associated MC (Figure 3—figure supplement 2). Furthermore, inhibition of SFK phosphorylation using PP2 (Varma et al., 2006) significantly reduced the number of F-actin foci (Figure 3B), indicating that TCR-driven SFK signaling is required for their formation. We conclude that F-actin foci correspond to sites of early TCR signaling and require active SFKs.


Actin foci facilitate activation of the phospholipase C-γ in primary T lymphocytes via the WASP pathway.

Kumari S, Depoil D, Martinelli R, Judokusumo E, Carmona G, Gertler FB, Kam LC, Carman CV, Burkhardt JK, Irvine DJ, Dustin ML - Elife (2015)

Localization of phosphorylated form of Src family kinases (SFK) at TCR MC/F-actin foci.AND mouse CD4 T cell blasts were labeled with Alexa568-H57 Fab, incubated with MHCp/ICAM1 containing bilayer for 2 min, fixed and then immunostained for phospho-SFK (p-SFK). An example line scan profile for the line (white) indicated on the left image is displayed (right graph) to show the relative distribution of TCR, actin and phospho-SFK across the row of pixels. Scale bar, 6 μm.DOI:http://dx.doi.org/10.7554/eLife.04953.022
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4355629&req=5

fig3s2: Localization of phosphorylated form of Src family kinases (SFK) at TCR MC/F-actin foci.AND mouse CD4 T cell blasts were labeled with Alexa568-H57 Fab, incubated with MHCp/ICAM1 containing bilayer for 2 min, fixed and then immunostained for phospho-SFK (p-SFK). An example line scan profile for the line (white) indicated on the left image is displayed (right graph) to show the relative distribution of TCR, actin and phospho-SFK across the row of pixels. Scale bar, 6 μm.DOI:http://dx.doi.org/10.7554/eLife.04953.022
Mentions: To further investigate the role of TCR signaling in foci formation, we examined the role of Src family kinases (SFK) signaling. TCR signaling proceeds by accumulation of active Lck, as indicated by phosphorylation of the activation loop, in MCs (Campi et al., 2005). Consistent with this, phospho-SFK localized to F-actin foci associated MC (Figure 3—figure supplement 2). Furthermore, inhibition of SFK phosphorylation using PP2 (Varma et al., 2006) significantly reduced the number of F-actin foci (Figure 3B), indicating that TCR-driven SFK signaling is required for their formation. We conclude that F-actin foci correspond to sites of early TCR signaling and require active SFKs.

Bottom Line: Yet, when WASP function is eliminated there is negligible effect on actin polymerization at the immunological synapse, leading to gaps in our understanding of the events connecting WASP and calcium ion signaling.These foci are polymerized de novo as a result of the T cell receptor (TCR) proximal tyrosine kinase cascade, and facilitate distal signaling events including PLCγ1 activation and subsequent cytoplasmic calcium ion elevation.We conclude that WASP generates a dynamic F-actin architecture in the context of the immunological synapse, which then amplifies the downstream signals required for an optimal immune response.

View Article: PubMed Central - PubMed

Affiliation: Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, United States.

ABSTRACT
Wiscott Aldrich Syndrome protein (WASP) deficiency results in defects in calcium ion signaling, cytoskeletal regulation, gene transcription and overall T cell activation. The activation of WASP constitutes a key pathway for actin filament nucleation. Yet, when WASP function is eliminated there is negligible effect on actin polymerization at the immunological synapse, leading to gaps in our understanding of the events connecting WASP and calcium ion signaling. Here, we identify a fraction of total synaptic F-actin selectively generated by WASP in the form of distinct F-actin 'foci'. These foci are polymerized de novo as a result of the T cell receptor (TCR) proximal tyrosine kinase cascade, and facilitate distal signaling events including PLCγ1 activation and subsequent cytoplasmic calcium ion elevation. We conclude that WASP generates a dynamic F-actin architecture in the context of the immunological synapse, which then amplifies the downstream signals required for an optimal immune response.

Show MeSH
Related in: MedlinePlus